The present invention relates to a printer, copier, facsimile apparatus, laser printer or similar image forming equipment and, more particularly, to a document feeder for feeding a plurality of kinds of documents to such equipment automatically and a finisher for sorting, stapling or otherwise finishing sheets on which images have been formed.
Image forming equipment of the kind described has to feed and process documents automatically in order to increase production efficiency. Especially, there is an increasing demand for versatile document handling functions, and a document feeder itself is becoming more complicated. Document feeders available today include one which has a single document tray and can feed a plurality of sets of documents to image forming equipment automatically if a special sheet is inserted between adjoining sets of documents. However, inserting such a sheet between each adjoining sets of documents is time- and labor-consuming. Using the extra sheet as a job sheet needs more time and labor and, moreover, prevents documents of different sizes from being positioned with accuracy. Japanese Patent Laid-Open Publication No. 252564/1986 discloses an apparatus which has a plurality of document trays and moves them to a document feeder one at a time by use of a spiral cam. Japanese Patent Laid-Open Publication No. 82249/1988 teaches an arrangement in which a group of document trays are moved to a document feed position by a pinion and rack device and brings documents to a feed position by using the inclination of the trays and stops. The problem with these schemes is that the spiral cam or the pinion and rack device has to be accompanied by complicated means for moving the document trays, resulting in poor productivity and reliability.
Conventional finishers for finishing sheets include a sorter and a stacker each having multiple bins and located downstream of, for example, a fixing unit of a copier with respect to an intended direction of sheet transport. When a sort mode is selected, the sorter stacks processed sheets, or copies, in order of page. In a stack mode operation, the stacker stacks copies page by page. A more advanced finisher has a stapler for stapling each sorted or stacked set of sheets automatically. This type of finisher, or sorter/stapler, may be so constructed as to sort sheets into multiple bins arranged one above another and staple the sheets stacked in each bin by a stapler which is movable relative to the bins. This kind of construction, however, has a problem that when the number of bins loaded with stapled sets of sheets is great, it takes a substantial period of time to bring the stapled sheets out of the such bins, noticeably reducing the efficiency of copying operations or image forming operations. In addition, productivity in the copying or image forming aspect is critically lowered since the next copying procedure cannot be started unless all the sheets ar removed from the bins. Another conventional sorter/stapler has sheet gripping means for gripping a set of sheets sorted into a bin and moving it from the bin to a stapling position where a stapler is located, as disclosed in Japanese Patent Laid-Open Publication No. 158465/1985. While the sheet gripping means is essential in such a sorter/stapler because the bins and the stapler are remote from each other, it makes the whole apparatus complicated and bulky. Further, a set of sheets sorted into a bin may be shifted to a staple tray, stapled on the staple tray, and then dropped into a stacker by gravity, as taught in Japanese Patent Laid-Open Publication No. 41363/1988. However, moving such sorted sets of sheets to the staple tray one by one is undesirable from the productivity standpoint. Moreover, the apparatus is complicated and bulky because the bin section and the staple section are independent of each other.